This invention relates generally to communication systems and more particularly to radio receivers used within such communication systems.
Communication systems are known to support wireless and wire lined communications between wireless and/or wire lined communication devices. Such communication systems range from national and/or international cellular telephone systems to the Internet to point-to-point in-home wireless networks. Each type of communication system is constructed, and hence operates, in accordance with one or more communication standards. For instance, wireless communication systems may operate in accordance with one or more standards including, but not limited to, IEEE 802.11, Bluetooth, advanced mobile phone services (AMPS), digital AMPS, global system for mobile communications (GSM), code division multiple access (CDMA), local multi-point distribution systems (LMDS), multi-channel-multi-point distribution systems (MMDS), and/or variations thereof.
Depending on the type of wireless communication system, a wireless communication device, such as a cellular telephone, two-way radio, personal digital assistant (PDA), personal computer (PC), laptop computer, home entertainment equipment, et cetera communicates directly or indirectly with other wireless communication devices. For direct communications (also known as point-to-point communications), the participating wireless communication devices tune their receivers and transmitters to the same channel or multiple channels (e.g., one or more of the plurality of radio frequency (RF) carriers of the wireless communication system) and communicate over that channel. For indirect wireless communications, each wireless communication device communicates directly with an associated base station (e.g., for cellular services) and/or an associated access point (e.g., for an in-home or in-building wireless network) via an assigned channel, or channels. To complete a communication connection between the wireless communication devices, the associated base stations and/or associated access points communicate with each other directly, via a system controller, via the public switch telephone network, via the internet, and/or via some other wide area network.
For each wireless communication device to participate in wireless communications, it includes a built-in radio transceiver (i.e., receiver and transmitter) or is coupled to an associated radio transceiver (e.g., a station for in-home and/or in-building wireless communication networks, RF modem, etc.). As is known, the receiver receives RF signals, demodulates the RF carrier frequency from the RF signals via one or more intermediate frequency stages to produce baseband signals, and demodulates the baseband signals in accordance with a particular wireless communication standard to recapture the transmitted data. The transmitter converts data into RF signals by modulating the data in accordance with the particular wireless communication standard to produce baseband signals and mixes the baseband signals with an RF carrier in one or more intermediate frequency stages to produce RF signals.
To recapture data from RF signals, a receiver includes a low noise amplifier, down conversion module and demodulation module. For radio frequency integrated circuits, it is desirable to provide the low noise amplifier with differential RF signals instead of single ended RF signals to improve noise performance and common mode rejection. To convert received single ended RF signals into differential RF signals, a receiver includes a balun (i.e., a balanced/unbalanced transformer).
Until very recently, the baluns were off-chip, i.e., on the printed circuit board, and were typically implemented in the form of micro-strip lines. Recent attempts to integrate a balun onto a radio frequency integrated circuit have had limited success. For example, parallel winding, inter-wound winding, overlay winding, single planar, square wave winding, and concentrical spiral winding on-chip baluns have been tried with limited success. Each of these on-chip baluns suffers from one or more of: low quality factor, (which causes the balun to have a relatively large noise figure); too low of a coupling coefficient (which results in the inductance value of the balun not significantly dominating the parasitic capacitance making impedance matching more complex); asymmetrical geometry (which results in degradation of differential signals); and a relatively high impedance ground connection at the operating frequency.
Therefore, a need exists for an integrated low noise amplifier that includes a symmetrical balun that has a low noise figure, low ground impedance at the operating frequency and has an inductance value that is dominant at the operating frequency.
The integrated circuit low noise amplifier disclosed herein substantially meets these needs and others. Such an integrated low noise amplifier includes an on-chip balun, a line impedance matching circuit and an on-chip differential amplifier. The on-chip balun is operably coupled to convert a single ended signal into a differential signal (e.g., a single ended RF signal into a differential RF signal). The line impedance matching circuit is operably coupled to the primary of the on-chip balun to provide impedance matching for a line carrying the single ended signal (e.g., provides impedance matching with the antenna). The on-chip differential amplifier is operably coupled to amplify the differential signal.
The on-chip differential amplifier may be constructed in a manner such that its input impedance approximately matches the output impedance of the on-chip balun. The integrated circuit low noise amplifier may further include a ground circuit operably coupled to the on-chip balun to compensate for bond wire and package inductance and resistance, which if uncompensated, provides a relatively high ground impedance at the operating frequency, or frequencies.
An alternate integrated circuit low noise amplifier includes an on-chip balun and an on-chip differential amplifier. The on-chip balun converts and amplifies a single ended RF signal into a gained differential RF signal. The on-chip differential amplifier is coupled to further amplify the gained differential RF signal. Such an integrated low noise amplifier may further include a line impedance matching circuit coupled to the primary of the on-chip balun and may further include a ground circuit to compensate for bond wire and package inductance and resistance.
The integrated circuit low noise amplifier in any embodiment may be utilized in a radio receiver of a wireless communication device. The low noise amplifier, within a receiver section, is operably coupled to receive single ended RF signals from an antenna and to provide amplified differential RF signals to a down conversion module. Such a low noise amplifier with integrated balun has a relatively low noise figure, a low ground impedance at the operating frequency, or frequencies, and has an inductance value of the balun at the operating frequency, or frequencies, that dominates the parasitic capacitance to simplify the line impedance matching.